UPD78F1502AGK-GAK-AX Datasheet, PDF (263/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 5 CLOCK GENERATOR
5.6.6 Condition before changing CPU clock and processing after changing CPU clock
Condition before changing the CPU clock and processing after changing the CPU clock are shown below.
Table 5-5. Changing CPU Clock (1/2)
CPU Clock
Before Change After Change
Internal high-
speed
oscillation clock
X1 clock
External main
system clock
Subsystem
clock
20 MHz internal
high-speed
oscillation clock
X1 clock
Internal high-
speed oscillation
clock
External main
system clock
Subsystem
clock
External main
system clock
20 MHz internal
high-speed
oscillation clock
Internal high-
speed
oscillation clock
X1 clock
Subsystem
clock
20 MHz internal
high-speed
oscillation clock
Condition Before Change
Stabilization of X1 oscillation
• OSCSEL = 1, EXCLK = 0, MSTOP = 0
• After elapse of oscillation stabilization time
Enabling input of external clock from
EXCLK pin
• OSCSEL = 1, EXCLK = 1, MSTOP = 0
Stabilization of X1 oscillation
• OSCSELS = 1, XTSTOP = 0
• After elapse of oscillation stabilization time
Stabilization of DSC oscillation with 20
MHz set by using the option byte
• VDD ≥ 2.7 V
• After elapse of oscillation stabilization
time (100 μs) after setting to DSCON = 1
• SELDSC = 1
Oscillation of internal high-speed oscillator
• HIOSTOP = 0
Transition not possible
(To change the clock, set it again after
executing reset once.)
Stabilization of XT1 oscillation
• OSCSELS = 1, XTSTOP = 0
• After elapse of oscillation stabilization time
Transition cannot be performed unless the
clock is changed to the internal high-speed
oscillation clock once.
Oscillation of internal high-speed oscillator
• HIOSTOP = 0
Transition not possible
(To change the clock, set it again after
executing reset once.)
Stabilization of XT1 oscillation
• OSCSELS = 1, XTSTOP = 0
• After elapse of oscillation stabilization time
Transition cannot be performed unless the
clock is changed to the internal high-speed
oscillation clock once.
Processing After Change
Operating current can be reduced by
stopping internal high-speed oscillator
(HIOSTOP = 1).
−
−
X1 oscillation can be stopped (MSTOP =
1).
−
X1 oscillation can be stopped (MSTOP =
1).
−
External main system clock input can
be disabled (MSTOP = 1).
−
External main system clock input can
be disabled (MSTOP = 1).
−
R01UH0004EJ0501 Rev.5.01
247
Jun 20, 2011